Hashes, references, modules (and the huge number of modules that are available for free), speed, documentation, etcetera etcetera.
What _technical_ reason would there be to use Ksh?

++ vs lbh qrpbqrq guvf hfvat n ge va Crey :)
Nabgure bar vs lbh qvq fb jvgubhg ernqvat n znahny svefg.
-- vs lbh hfrq OFQ pnrfne ;)
    - Whreq